feat: telemetry data integrity — source tagging, UUID fingerprint, duration guards

- Add source field (live/test/dev) to telemetry pipeline: --source flag in
  gstack-telemetry-log, GSTACK_TELEMETRY_SOURCE env fallback, pass-through
  in telemetry-sync, source=eq.live filter on all dashboard queries
- Replace SHA-256 installation_id with UUID install_fingerprint for all tiers
  (not just community). Expand-contract migration: ADD new column + trigger
  to copy installation_id, preserving backward compat with old clients
- Fix duration bug: persist _TEL_START to file via $PPID (stable across bash
  blocks), cap durations at 86400s, reject negative values
- Ungate update-check pings from telemetry=off — sends only version + OS +
  random UUID. Generate .install-id in update-check for telemetry=off users
- Migration 003: source columns, install_fingerprint, duration CHECK
  constraint, indexes, recreated views with source filter, growth funnel
  (first-seen based), materialized views for daily installs + version adoption
- E2E test isolation: session-runner sets GSTACK_TELEMETRY_SOURCE=test
- 8 new telemetry tests (source field, duration caps, fingerprint persistence)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bin/gstack-telemetry-sync

@@ -76,19 +76,16 @@ while IFS= read -r LINE; do
   echo "$LINE" | grep -q '^{' || continue
 
   # Strip local-only fields + map JSONL field names to Postgres column names
+  # Backward compat: map old installation_id → install_fingerprint for unsent entries
   CLEAN="$(echo "$LINE" | sed \
     -e 's/,"_repo_slug":"[^"]*"//g' \
     -e 's/,"_branch":"[^"]*"//g' \
     -e 's/"v":/"schema_version":/g' \
     -e 's/"ts":/"event_timestamp":/g' \
     -e 's/"sessions":/"concurrent_sessions":/g' \
+    -e 's/"installation_id":/"install_fingerprint":/g' \
     -e 's/,"repo":"[^"]*"//g')"
 
-  # If anonymous tier, strip installation_id
-  if [ "$TIER" = "anonymous" ]; then
-    CLEAN="$(echo "$CLEAN" | sed 's/,"installation_id":"[^"]*"//g; s/,"installation_id":null//g')"
-  fi
-
   if [ "$FIRST" = "true" ]; then
     FIRST=false
   else